轿车排气噪声的准定常CFD研究

Investigation on Exhaust Noise Based on Quasi-steady CFD Method

采用2种方案建立了某轿车排气谐振器和消声器模型。针对方案1模型在某工况下进行的定常与非定常对比表明,发动机排气流动可近似为准定常过程。对2种方案发动机排气流动进行的准定常及宽频带声场分析表明,排气质量流率一定时加速阶段比减速阶段的传递损失大;与方案1相比,方案2大多数工况下的传递损失和压力损失小,但在急加速初期传递损失要大2.2dB(A);在快速松开加速踏板时传递损失要大1～1.9dB(A),而压力损失降低15%～45%。

The exhaust resonator and muffler model were established by using two different schemes.The steady and unsteady comparisons of 1# scheme show that engine exhaust flow may be considered as quasi-steady process.The quasisteady and broadband acoustic fields of engine exhaust flow for two different schemes were analyzed,the results show that the transmission loss of accelerating stage was more than that of decelerating stage at the same airflows mass flux,in the most engine operating conditions,the pressure loss and the transmission loss of 1# scheme were more than those of 2# scheme,but the transmission loss of 2# scheme increased by 2.2 dB（A） at the initial accelerating stage and 1-1.9 dB（A） at the decelerating stage respectively,the pressure transmission loss also reduced by 15 %-45 % at the decelerating stage.